The invention relates to multi-nozzle fluid jet looms, and more particularly for facilities in such looms for cyclically routing a propelling fluid to successive ones of the nozzles for conveying a weft thread along an operating path to be inserted into a shed of the loom.
Conventionally, fluid cycling systems of this type have employed cam-controlled slide valves which, being purely mechanical, have several disadvantages. Among such disadvantages is the fact that the rate of switching of the fluid among the successive nozzles can be adjusted, if at all, only by initially stopping the machine, so that adjustments of the weft insertion operation is extremely slow. Moreover, such mechanical types of fluid distributors are clumsy to mount, and have been found to be grossly inefficient, with leakage and hydraulic losses frequently amounting to 50-70% of the pressure gradient.
In an attempt to alleviate the disadvantages of such all-mechanical fluid distributor designs, a cycling system has been devised wherein a plurality of electromagnetically operated, normally closed valves are individually associated with the successive nozzles. In such system, the valves are operated in sequence at a preselected time for a suitable interval normally chosen to permit the weft to be propelled from one nozzle to the succeeding nozzle. In order to operate the respective valves, a plurality of sensors have been individually disposed at successive points along the operating path of the weft, each sensor being arranged to initiate an operating pulse for the associated valve when the weft has been propelled for a suitable interval along such path.
The last-mentioned system, in which each of such sensors are individually associated with a separate one of the valves, has proved to be quite complicated and expensive, particularly where such sensors have been assigned the task of not only initiating the operation of the associated valve, but also of terminating the operation of such valve.